CHAPTER TOOLS

Keywords:

Space plasmas—Mathematical models;

Magnetosphere—Mathematical models;

Ionosphere—Mathematical models

Summary

Recent observations that are relevant to models of the magnetotail and its coupling to the ionosphere are summarized. In particular observations in the near-earth plasma sheet and magnetotail lobes are reviewed. The two principal current sheets in the plasma sheet are located at the neutral sheet and the lobe-plasma sheet interface. The concept of plasmoid formation in the near-earth plasma sheet is critically examined in the context of new measurements of auroral oval motions and of plasma convection near the center plane of the plasma sheet. Global images of earth's polar cap are employed, together with simultaneous determination of the solar wind parameters, to demonstrate the storage and release of magnetotail energy prior to and following the onset of a magnetic substorm. During sustained periods of northward-directed interplanetary magnetic fields, auroral activity is most significant at latitudes poleward of a relatively quiescent auroral oval. The striking configuration of auroral luminosities known as a theta aurora can appear during these periods. It seems unlikely that the sometimes sought ground state of little or no ionospheric coupling with magnetotail plasmas and convection occurs with periods of northward interplanetary field. Instead the ionosphere-magnetotail system is actively coupled in the polar ionosphere.